From an Inbox, tap the icon to the left of the message(s) to delete.
Message(s) marked for deletion when the icon changes to a check mark.
Tap the Delete icon(located at the top).
To reverse the deletion, immediately tap UNDO once it appears at bottom of screen.
To delete all messages at once, access the email provider's website from a computer (if available). This process can't be completed from the tablet.